Between 18 and 23 September 2025, the US Patent Trial and Appeal Board (PTAB) issued final decisions invalidating Johns Hopkins University’s 11,339,219 (IPR2024-00625), 11,649,287 (IPR2024-00647), 11,629,187 (IPR2024-00649) and 11,634,491 (IPR2024-00650) in four inter partes review proceedings (IPRs) brought by MSD. JHU subsequently filed an appeal in relation to Patent 11,649,287 (IPR2024-00647) on 7 October 2025.
The four JHU patents relate to the use of pembrolizumab in treating cancer patients with high mutational burdens, such as those found in microsatellite instability high (MSI) or DNA mismatch repair deficient cancer (dMMR). The PTAB found that the patents were invalid for lack of novelty and/or obviousness based on prior art including a record of a JHU phase 2 clinical trial of Keytruda® (pembrolizumab) in MSI/dMMR cancer.
The four IPRs are a subset of nine IPRs filed by MSD against JHU patents in 2023 – 2024. One of the IPRs had previously been determined in June 2025, finding US 11,591, 393 invalid. The remaining four IPRs remain pending:
- 10,934,356 (IPR2024-00622), 11,325,974 (IPR2024-00623), 11,325,975 (IPR2024-00624): filed on 4 March 2024 and instituted on 23 September 2024; and
- 11,643,462 (IPR2024-00648): petition filed 13 March 2024, IPR instituted 3 October 2024.
In November 2022, MSD filed a complaint in the United States District Court (District of Maryland) against JHU seeking declarations of breach of contract, non-infringement and promissory estoppel. Based on the complaint, the dispute arose out of a contract between MSD and JHU to design and conduct a clinical trial on administration regimes for Keytruda® (pembrolizumab) in cancer patients with certain genetic biomarkers. JHU filed a counter-claim on 12 April 2023, including alleging infringement of each of the patents subject to the IPR proceedings referred to above. The US Court proceeding has been stayed pending the outcome of the IPRs. No trial date has been scheduled.